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In order to solve the VLE problem Need models for  i in each phase Examples of models of  i in the vapor phase Examples of models of  i in the liquid phase

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Now we are going to learn: Partial molar properties Because the chemical potential is a partial molar property At the end of this section think about this – What is the chemical potential in physical terms – What are the units of the chemical potential – How do we use the chemical potential to solve a VLE (vapor-liquid equilibrium) problem

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solution Calculate total molar volume of the 30% mixture We know the total volume, calculate the number of moles required, n Calculate n 1 and n 2 Calculate the total volume of each pure species needed to make that mixture

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Note curves for partial molar volumes

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From Gibbs-Duhem: Divide by dx1, what do you conclude respect to the slopes?

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Example 11.4 Given H=400x x 2 +x 1 x 2 (40x 1 +20x 2 ) determine partial molar enthalpies as functions of x 1, numerical values for pure-species enthalpies, and numerical values for partial enthalpies at infinite dilution Also show that the expressions for the partial molar enthalpies satisfy Gibbs-Duhem equation, and they result in the same expression given for total H.